Apparatus for separating sulphurous acid from sulphite waste liquor



June 25, 1935.- K. HEINEMANN 2,006,138

APPARATUS FOR SEPARATING SULPHUROUS ACID FROM SULPHITE WASTE LIQUOR I Filed April 26, 1954 Patented June 25, 1935 PATENT OFFICE APPARATUS FOR SEPARATING SULPHUR- OUS ACID LIQUOR FROM SULPHITE WASTE Karl Heinemann, deceased, late of Dresden, Germany, by Auguste ecutrix, Dusseldorf, American Lurgi Corp a corporation of New Application April 26,

In Germany 3 Claims.

The present invention relates to an apparatus for the separation of sulphurous acid from. sulphite waste liquor.

It is well known that the degasifiers used in the pulp industry only partly fulfill their intended purposes. Even recently it has been-proposed to reconstruct old digesters and drums of shut-down fire-tube boilers into degasifiers because it has been the belief of those skilled in the art that the larger the degasifier, the better its effect. Achenbach in his patented spray degasifier has selected a capacity-of 1/7 of that of the digester. Unfortunately the Achenbach degasifier has the disadvantage that the pulp fibres carried away with the liquor are apt to clog up the small discharge outlets. The old large capacity degasifiers not only have the disadvantage of incomplete degasification but also of high maintenance charges. Although many proposals have been made, none, as far as I am aware, has been wholly satisfactory and acceptable in industrial practice.

It has been discovered that it is possible to achieve a better degasification than heretofore and to conduct the process in a relatively small space, whereby considerable savings in installation costs may be effected.

It is an object of the present invention to provide an improved degasifier which embodies a trickling system capable of efliciently effecting evaporation and the liberation of gases containing sulphur dioxide from the liquor under treatment.

It is a further object of the invention to provide a degasifier for the separationpf sulphur dioxide containing gases from sulphite waste liquor which involves the use of a plurality of super-imposed devices which effectively cause the splashing of the liquor and the flowing thereof through a tortuous path whereby the liquor can be effectively cooled and the sulphur dioxide containing gases liberated therefrom.

A further object of the invention is to provide a degasifier which is protected against excessive pressures and which is protected against vacuum.

Other objects and advantages of the invention will become apparent from the following description taken in conjunction with the drawing which shows in a vertical section apreferred embodiment for carrying the invention into practice.

According to the present invention, the trickling system consists of a set of superimposed rings and plates spaced from each other by certain distances. The sprayed liquor is conducted from Elizabeth Heinemann, ex-

Germany, assignor to oration, New York, N. 5.,

York

1934, Serial No. 722,469

July 11, 1935) above to the trickling system and falls from a ring to the next lower plate until the liquor has traversed the entire system, while the gas is permitted to escape through the space between the adjacent rings. By means of this construction, the discharge of the liquor is limited to the core zone of the degasifier. The sulphur dioxide containing gases still remaining in the liquor are very easily eliminated through the impact of the liquor which has previously been divided into a veil of liquid or a plurality of separate jets with the deflection plates. The freed gases may then escape via the shortest route. The contact between gas and liquor is herein limited to the smallest extent, which is in contrast to the known degasiiiers.

For the purpose of giving those skilled in the art a better understanding of the invention,-the following description of a preferred procedure will be given in conjunction with an illustrative embodiment of the invention.

The reference character (a) designates a metal vessel of rust proof steel, lead-coated iron or other suitable metal or alloy. The liquor to be degasified is introduced into vessel (a) through a conduit (b) which has an up-turned discharge nozzle (0) at the end thereof. The liquor from the nozzle is directed towards a deflection plate and rim ((1) extending vertically from the edge of the plate. The plate may be supported horizontally over nozzle (0) at a convenient distance -thereof, for instance, by fastening it in any convenient manner to the lower end of a vertical outlet pipe (2') for the removal of the gas mixture. Projecting inwardly from the inner periphery of rim (d) is a plurality of spaced lugs (e) which cause the distribution of the liquor in a ringelike formation of falling jets. The intermediate spaces thus formed between the jets permit immediate escape of gases from the liquor. Of course, the nozzle may also be pointed downwardly and the deflection plate or a perforated plate may be arranged below it.

The liquor falls into the trickling system, which in the embodiment illustrated comprises a plurality of superimposed rings (1) and plates (9). These rings and plates may be fastened by means of a frame to the lower or to the upper part of the apparatus. In this manner, the impact and heat effects are not transferred to the housing or vessel (a).

The liquor in its downward flow is alternately directed towards the center and again distributed outwardly, so.that a continuous and thorough mixing occurs. Fresh portions of liquor in a thin the vessel. Ultimately, the gas mixture escapes.

layer are available to come in contact with vapor and the duration of contact can be influenced by the number of rings and plates. The gas mixture escapes through the annular spaces (h) between adjacent rings into the outer zone located between the outside of the rings and the inside of through an outlet (2') The trickling system can, depending upon the mixture in the lower part of the vessel and the speed, be designed with a larger diameter towards the bottom, whereby the vapor and gas zone becomes narrower and the distributing capacity of the system for the liquor in relation to its lower evaporating capacity larger.

Since excess pressure in the vessel during the operation is subjected to strong fluctuations it must be taken care of. Often excess pressure can even be relieved by means easier than a rather high vacuum. Care should be taken to maintain the liquor level in the apparatus practically constant. Heretofore, the lower liquid seal was subject'to becoming filled with liquor. In the first event, the gas mixture would be carried away into the drains and in the second the effectiveness 01' the apparatus would be reduced. The aforesaid shortcomings can among other things be prevented by inserting a liquid trap comprising a chamber (k) and upstanding pipe (n) connected to the bottom thereof, the gas chamber (k) of which is placed by means of the pipe line (u) via chamber under the same pressure as the degasifler. Through the pipe line (u), the sulphur dioxide gases and vapors which are liberated in chamber (7" of the liquid trap progress through chamber (0) into the degasiiler where they are mixed with the gas mixture freed from the sprayed and drizzled liquor.

The U-shaped connecting pipe (I) practically eliminates the occurrence of strong fluctuations in the liquor level in the apparatus. When disturbances occur, liquor goes over to the separator (It) which is connected to an upstanding pipe (11). This pipe is in communication with the atmosphere via a vertical pipe (m).

- Much more dangerous than the occurrence of the excess pressure is the formation of vacuum which may occur, for instance, when liquor charging stops. To prevent this, the thin-walled ape paratus made, for example, of rust proof steel, must absolutely be protected. For economic reasons the degasifier cannot be built with sufliciently thick walls. Although a liquid seal can be provided for this purpose, such a device is always somewhat slow in response. It is preferred to use a disc valve which is light as possible. The valve port (p) in the casing (0) must have a large tree cross sectional area and the lightly constructed disc valve (q), which rests freely on this port, must have a correspondingly large area. If in the degasifler a vacuum is created, the .disc valve (q) is immediately lifted by the outside air pressure. Air from the atmosphere enters the degasiher and destroys the vacuum, thus preventing the collapse of the degasifler. A protection against gumming up of the disc valve and consequent prevention of free mobility of the valve for the compensation of the vacuum is prevented by constantly rinsing the guiding pipe (r) 01' the valve spindle (8) through pipe (t) with hot water. Cold water does not dissolve the gum, etc. so well and would absorb acid from the steam chamber.

The discharge takes place either in the apparatus,

the separator or through a siphon into the open.

What is claimed is:

1. A degasiiler for separating sulphur dioxide containing gases from waste sulphite liquor which comprises a cylindrical vessel, a plurality of superimposed rings and plates mounted in said vessel, an inlet nozzle mounted over said rings and plates, an outlet for the withdrawal of sulphur dioxide containing gases, a liquor outlet at the bottom of said vessel, a U-shaped pipe associated with liquor outlet, a trap connected to said pipe, 9. connection between the top of said vessel and said trap for'equalizing the pressure, and a disc valve in said connection for admitting air from the atmosphere to said vessel when the latter is under vacuum.

2. A degasifier for separating sulphur dioxide containing gases from waste sulphite liquor which comprises a cylindrical vessel, a plurality of superimposed rings and plates mounted in said vessel, an inlet nozzle mounted over said rings and plates, an outlet for the withdrawal 0! sulphur dioxide containing gases, a liquid outlet at the bottom of said vessel, a U-shaped pipe associated with the liquid outlet, a trap connected to said pipe, said trap comprising a gas chamber and an upstanding pipe extending from the lower porticn thereof and connected to the atmosphere, a connection between the top of said vessel and said trap for equalizing the pressure, and a disc valve in said connection for admitting air from the atmosphere to said vessel when the latter is under vacuum.

3. A degasifier for separating sulphurv dioxide containing gases from waste sul'phite liquor which comprises a cylindrical vessel, a plurality of superimposed rings and plates mounted in said vessel, an inlet nozzle mounted over said rings and plates, an outlet for the withdrawal of sul phur dioxide containing gases, a-liquor outlet at the bottom of said vessel, a U-shaped pipe associated with liquor outlet, a trap connected to said pipe, a connection between the top of said vessel and said trap for equalizing the pressure, and a disc valve in said connection for admitting air from the atmosphere to said vessel when the latter is under vacuum and means ior rinsing said valve.

AUGUS'I'E ELIZABETH HEINEMANN,

Executrix of the Estate of Karl Heinemann, De-' ceased. 

